[clang] [clang][Preprocessor] Fix expansion locations for feature-like builtin macros (PR #207130)

[Macro Terra via cfe-commits]

https://github.com/hongtaihu updated https://github.com/llvm/llvm-project/pull/207130

>From 30cc618a32fdf8374d9b108f7788cf7e1731bdf1 Mon Sep 17 00:00:00 2001
From: hongtaihu <13541229370 at qq.com>
Date: Thu, 2 Jul 2026 14:43:32 +0800
Subject: [PATCH] [clang][Preprocessor] Fix expansion locations for
 feature-like builtin macros

Fixes #196067.

This patch fixes the expansion locations of synthesized tokens produced by feature-like builtin macros such as `__has_builtin(...)`.

Feature-like builtin macros lex past the macro name while evaluating their arguments. `ExpandBuiltinMacro()` used the final `Tok` location as both the expansion start and end when creating the synthesized result token, so `__has_builtin(...)` results were anchored at the closing paren rather than the builtin macro invocation.

Fix by saving the macro-name location before argument parsing and using it as the expansion start. The expansion end remains the final `Tok` location.

Add a `syntax::TokenCollector` regression test for a valid `__has_builtin(...)` expansion and the `__is_identifier;` recovery path.

Assisted-by: OpenAI Codex
---
 clang/lib/Lex/PPMacroExpansion.cpp            |  3 ++-
 clang/unittests/Tooling/Syntax/TokensTest.cpp | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Lex/PPMacroExpansion.cpp b/clang/lib/Lex/PPMacroExpansion.cpp
index 23a21f42b8e3a..e09e80a063c4e 100644
--- a/clang/lib/Lex/PPMacroExpansion.cpp
+++ b/clang/lib/Lex/PPMacroExpansion.cpp
@@ -1619,6 +1619,7 @@ void Preprocessor::ExpandBuiltinMacro(Token &Tok) {
   // Figure out which token this is.
   IdentifierInfo *II = Tok.getIdentifierInfo();
   assert(II && "Can't be a macro without id info!");
+  SourceLocation MacroNameLoc = Tok.getLocation();
 
   // If this is an _Pragma or Microsoft __pragma directive, expand it,
   // invoke the pragma handler, then lex the token after it.
@@ -2096,7 +2097,7 @@ void Preprocessor::ExpandBuiltinMacro(Token &Tok) {
   } else {
     llvm_unreachable("Unknown identifier!");
   }
-  CreateString(OS.str(), Tok, Tok.getLocation(), Tok.getLocation());
+  CreateString(OS.str(), Tok, MacroNameLoc, Tok.getLocation());
   Tok.setFlagValue(Token::StartOfLine, IsAtStartOfLine);
   Tok.setFlagValue(Token::LeadingSpace, HasLeadingSpace);
   Tok.clearFlag(Token::NeedsCleaning);
diff --git a/clang/unittests/Tooling/Syntax/TokensTest.cpp b/clang/unittests/Tooling/Syntax/TokensTest.cpp
index ae5001a2f5645..5efe52a9cbbb9 100644
--- a/clang/unittests/Tooling/Syntax/TokensTest.cpp
+++ b/clang/unittests/Tooling/Syntax/TokensTest.cpp
@@ -552,6 +552,25 @@ file './input.cpp'
   }
 }
 
+TEST_F(TokenCollectorTest, FeatureLikeBuiltinMacros) {
+  recordTokens("__has_builtin(__builtin_allow_runtime_check)\n");
+  EXPECT_THAT(Buffer.expandedTokens(),
+              ElementsAre(AllOf(Kind(tok::numeric_constant), HasText("1")),
+                          Kind(tok::eof)));
+  auto ExpansionRange =
+      SourceMgr->getExpansionRange(findExpanded("1").front().location());
+  auto MacroInvocation =
+      findSpelled("__has_builtin ( __builtin_allow_runtime_check )");
+  EXPECT_EQ(MacroInvocation.front().location(), ExpansionRange.getBegin());
+  EXPECT_EQ(MacroInvocation.back().location(), ExpansionRange.getEnd());
+
+  AllowErrors = true;
+  recordTokens("__is_identifier;\n");
+  EXPECT_THAT(Buffer.expandedTokens(),
+              ElementsAre(AllOf(Kind(tok::numeric_constant), HasText("0")),
+                          Kind(tok::eof)));
+}
+
 TEST_F(TokenCollectorTest, SpecialTokens) {
   // Tokens coming from concatenations.
   recordTokens(R"cpp(